The Department of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA) has ordered Exxon Mobil Corporation to rebury the Silvertip pipeline underneath the Yellowstone River's bed to protect the line from damage. PHMSA also said the company will need to submit a restart plan before it can resume operation of the pipeline. In its order, the PHMSA told Exxon to use horizontal drilling methods to rebury the pipeline at the river crossing to protect the pipeline from external damage. The company also must devise a plan to operate and monitor the pipeline during flooding conditions, including increasing patrols and surveillance. PHMSA regulates pipeline companies to ensure that energy is delivered safely to U.S. households and businesses.

Approximately 750 and 1,000 barrels of oil spilled into the Yellowstone River near Billings, Montana, after the 12-inch pipeline ruptured late Friday amid high waters, according to preliminary findings issued by the PHMSA. The agency said spilled oil in the river has traveled as far as 240 miles downstream to Terry, Montana. Exxon reported in June that at the river crossing, the pipe lay at least 12 feet below the surface.

The 69-mile pipeline delivers oil to Exxon's Billings refinery, which sits adjacent to the Yellowstone River. The facility processes crude oil from Wyoming and Alberta into gasoline and ultralow-sulfur diesel fuel, according to Exxon's website. The section of the pipeline that crosses the river, near the site of the accident, was built in 1991, although original portions of the pipeline were built between 1949 and 1954, the PHMSA said.

Exxon doesn't yet have a repair plan in place for the Silvertip pipeline. The company doesn't know when the crude-oil pipeline, which usually moves about 40,000 barrels of oil a day, could be back online, nor how much it will cost to clean up the spill.

The PHMSA has been working with the U.S. Environmental Protection Agency and the U.S. Coast Guard to investigate the incident and determine the cause of the pipeline rupture. (WSJ, 7/6/2011)